Outboard drive for boats

ABSTRACT

Outboard drive for boats, including a gear housing, an underwater housing connected rotatably to the gear housing, and a mounting element arranged between the gear housing and the underwater housing for mounting the drive in a boat hull with the gear housing on the inside and the underwater housing on the outside of the hull and including an exhaust passage with an exhaust outlet. The exhaust outlet is surrounded by a plate made of polytetrafluoroethylene fixed on the underside of the mounting element. The underwater housing is rotatable relative to the gear housing by an electric servomotor communicating with a control computer, which communicates with an engine control computer for an internal combustion engine connected to the drive and is arranged so as, when the engine is shut off, to give a signal to the servomotor to put the underwater housing in a position corresponding to moving straight ahead.

The present invention relates to an outboard drive for boats for drivingat least one propeller, comprising a gear housing, an underwater housingconnected rotatably to the gear housing, mounting means arranged betweenthe gear housing and the underwater housing for mounting the drive in aboat hull with the gear housing on the inside and the underwater housingon the outside of the hull and comprising an exhaust passage, which hasan exhaust outlet opening into an exhaust inlet to an exhaust passage inthe underwater housing, and power-operated means which are connected toan electronic control unit and by means of which the underwater housingis rotatable relative to the gear housing and the mounting meansdepending on control commands fed into the control unit.

Outboard drives of the kind indicated above are known, for example fromSE-A-522 187. Compared with the more common stem-mounted outboarddrives, it is characteristic of these drives that the underwater housingcannot, as in the case of the former drives, be tipped up out of thewater, for example when the boat is left stationary for a relativelylong time. They are consequently more susceptible to fouling byorganisms in the water, for example acorn barnacles. Underwater housingsmade of cast metal, in particular bronze, which are used in the typedescribed in the publication mentioned above, are especiallysusceptible. For example, acorn barnacles attach themselves so firmlythat they have to be cut away.

In a known type of outboard drive of the kind indicated above, sealingsurfaces around the exhaust outlet in the mounting means lie directly infront of sealing surfaces around the exhaust outlet in the underwaterhousing when moving straight ahead. When large steering deflections areperformed, however, the exhaust outlet, and thus parts of the sealingsurfaces as well, will be at least partly exposed, the exhaust gasesthrough the exhaust outlet being blown out at least in part at the sideof the exhaust inlet in the underwater housing. When putting-inmanoeuvres are performed, great rudder deflections are often necessary,and, if the boat is left with a great steering deflection of theunderwater housing after putting-in, the sealing surfaces are accessibleto fouling which after a relatively long time, for example a month, canbecome extensive, which leads to greater steering force from thesteering machinery being necessary and to the power consumption, thewear and the service requirement increasing.

The object of the present invention is to produce an outboard drive ofthe kind referred to in the introduction which eliminates the problem offouled sealing surfaces around the exhaust outlet and inlet.

According to the invention, this is achieved by virtue of the fact thatthe said exhaust outlet is surrounded by a surface layer whichcounteracts fouling by organisms present in the water and that thecontrol unit is arranged so as, on a given control command, via thepower-operated means, to put the underwater housing in a predeterminedposition in which a surface of the underwater housing, which surfacefaces the exhaust outlet and surrounds the said exhaust inlet, lieswithin the surrounding boundary of the said surface layer.

By, in accordance with a preferred embodiment of the invention,arranging a sheet of Teflon® (polytetrafluoroethylene) which covers thatregion of the mounting means facing the underwater housing between theend positions of the underwater housing and having the engine controlunit for a drive engine coupled to the drive give a control command tothe control unit of the drive to put the drive in a position halfwaybetween these end positions, that is to say the position for movingstraight ahead, when the engine is shut off, the problems of foulingdescribed above are eliminated automatically without the personresponsible for the boat having to take any special action. Organismssuch as, for example, acorn barnacles attach themselves very weakly toTeflon,

The invention is described in greater detail with reference toillustrative embodiments shown in the accompanying drawing, in which

FIG. 1 shows a perspective view of an embodiment of an outboard driveaccording to the invention, and

FIG. 2 shows a longitudinal section through a part of the outboard drivein FIG. 1.

The propeller drive designated generally by 1 in FIG. 1 has a gearhousing 2 enclosing a horizontal drive shaft, a vertical drive shaft andan intermediate bevel gear (not shown). The horizontal drive shaft isintended to be connected to a drive engine, and the vertical drive shaftto a vertical drive shaft (not shown) which is mounted in an underwaterhousing 3 and, via a bevel gear in the underwater housing 3, drives twoconcentric counter-rotating propeller shafts (not shown), each with arespective propeller 4 and 5.

Arranged between the upper gear housing 2 and the underwater housing 3is a mounting element designated generally by 6 which consists of on theone hand a lower bowl-shaped housing part 7, which is connected firmlyto the gear housing 2 in a way not shown in greater detail, and on theother hand an upper housing part 8 which, when the drive 1 is mountedthrough an opening in the bottom of a boat, is bolted to the lowerhousing part 7. Sealing rings 11 and 12 are arranged between conicalsurfaces 9 and 10 on respective housing parts 7 and 8.

The underwater housing 3 is mounted rotatably in the gear housing 2 in aknown way. The rotary movement is brought about with the aid of anelectric servomotor unit 13 which is assembled together with the gearhousing 2 and, via an integrated planetary gear, rotates the underwaterhousing 3 relative to the gear housing depending on signals from anelectronic control unit in the form of a control computer 14 which, in apractical embodiment, is also integrated in the servomotor unit 13. Inthe embodiment shown, the control computer 14 communicates with anengine control computer 15 for an internal combustion engine, forexample a diesel engine, (not shown) connected to the drive.

The control computer 14 is arranged so as, on a signal from the enginecontrol computer 15 indicating a command to stop the internal combustionengine (ignition off), to give a signal to the servomotor to put theunderwater housing 3 in a position halfway between two end positions,that is to say in the straight-ahead position. FIG. 1 shows an endposition at 16, when the underwater housing 3 is in a position formaximum starboard yaw, that is to say in the opposite end position.

As can be seen from FIG. 1, an exhaust pipe 20 from the internalcombustion engine (not shown) is connected to the mounting element 6.The exhaust pipe 20 opens into an exhaust passage 21 (FIG. 2) whichextends through the element 6 and, on the underside of the element 6,has an outlet opening 22 which, in the position shown in FIG. 1 of theunderwater housing 3, is partly exposed, so that exhaust gases are blownin part directly out into the water and in part through an exhaustpassage 23 in the underwater housing 3. The passage 23 has an inlet 24which, in the position of the underwater housing for moving straightahead, that is to say halfway between the end positions 16, liesdirectly in front of the outlet opening 22 in the mounting element 6.The passage 23 opens into an exhaust discharge 26 in the aft side of theunderwater housing 3.

The sector between the end positions 16 on the underside of the mountingelement 6 is covered by a fouling-preventing layer, preferably a plate27 made of polytetrafluoroethylene (Teflon®), which is bolted to themounting element 6 and has an opening 28 which coincides with the outletopening 22. It has been found that even if water organisms, such asacorn barnacles, do after a relatively long time stationary becomeattached to the plate 27 on those surfaces which are not covered by theunderwater housing in its straight-ahead position, they are neverthelessattached so loosely that they are easily scraped off by the underwaterhousing 6 when this is rotated during steering the next time the boat istaken out.

It is also conceivable, as an alternative to the model described aboveof having engine shut-off bring the underwater housing 3 intostraight-ahead position, to arrange a separate manual control 30 whichhas a “parking position” in which the underwater housing is put in thestraight-ahead position. A disadvantage of a separate manual control isof course that it is possible to forget to put it in the parkingposition just as it is also possible to forget to put it in the “offposition” when starting the next time.

In a drive with the engine control function described above, which alsohas a brake for locking the underwater housing in the set position afterthe engine has been shut off, the engine control computer is alsoarranged so as to switch the brake off automatically via the controlcomputer of the drive when the engine is started.

1. Outboard drive for boats for driving at least one propeller,comprising a gear housing, an underwater housing connected rotatably tothe gear housing, mounting means arranged between the gear housing andthe underwater housing for mounting the drive in a boat hull with thegear housing on the inside and the underwater housing on the outside ofthe hull and comprising an exhaust passage, which has an exhaust outletopening into an exhaust inlet to an exhaust passage in the underwaterhousing, and power-operated means which are connected to an electroniccontrol unit and by means of which the underwater housing is rotatablerelative to the gear housing and the mounting means depending on controlcommands fed into the control unit, wherein the exhaust outlet issurrounded by a surface layer which counteracts fouling by organismspresent in the water and the control unit is arranged so as, on a givennon-steering control command, via the power-operated means to put theunderwater housing in a predetermined position in which a surface of theunderwater housing, which surface faces the exhaust outlet and surroundsthe exhaust inlet, lies within the surface layer.
 2. Outboard driveaccording to claim 1, wherein the underwater housing is rotatablebetween two predetermined end positions and in that the surface layercovers the surface region between these end positions.
 3. Outboard driveaccording to claim 2, wherein the predetermined position of theunderwater housing lies halfway between the end positions.
 4. Outboarddrive according to claim 3, wherein the surface layer consists ofpolytetrafluoroethylene.
 5. Outboard drive according to claim 3, whereinthe control unit communicates with an engine control unit for aninternal combustion engine and is arranged so as, on a signal to theengine control unit to shut off the internal combustion engine, to givea control command to the power-operated means to put the underwaterhousing in the predetermined position.
 6. Outboard drive according toclaim 3, wherein the control unit communicates with a manual controlwhich, when operated manually, gives the control unit a control commandto put the underwater housing in the predetermined position.
 7. Outboarddrive according to claim 3, wherein the control unit is a controlcomputer, in which the value of the steering angle of the underwaterhousing relative to the gear housing in the predetermined position isstored.
 8. Outboard drive according to claim 2, wherein the surfacelayer consists of polytetrafluoroethylene.
 9. Outboard drive accordingto claim 2, wherein the control unit communicates with a manual controlwhich, when operated manually, gives the control unit a control commandto put the underwater housing in the predetermined position. 10.Outboard drive according to claim 2, wherein the control unit is acontrol computer, in which the value of the steering angle of theunderwater housing relative to the gear housing in the predeterminedposition is stored.
 11. Outboard drive according to claim 1, wherein thesurface layer consists of polytetrafluoroethylene.
 12. Outboard driveaccording to claim 11, wherein the control unit communicates with anengine control unit for an internal combustion engine and is arranged soas, on a signal to the engine control unit to shut off the internalcombustion engine, to give a control command to the power-operated meansto put the underwater housing in the predetermined position. 13.Outboard drive according to claim 11, wherein the control unitcommunicates with a manual control which, when operated manually, givesthe control unit a control command to put the underwater housing in thepredetermined position.
 14. Outboard drive according to claim 11,wherein the control unit is a control computer, in which the value ofthe steering angle of the underwater housing relative to the gearhousing in the predetermined position is stored.
 15. Outboard driveaccording to claim 1, wherein the control unit communicates with amanual control which, when operated manually, gives the control unit acontrol command to put the underwater housing in the predeterminedposition.
 16. Outboard drive according to claim 1, wherein the controlunit is a control computer, in which the value of the steering angle ofthe underwater housing relative to the gear housing in the predeterminedposition is stored.
 17. Outboard drive according to claim 1, wherein thepower-operated means are an electric servomotor.
 18. Outboard drive forboats for driving at least one propeller, comprising a gear housing, anunderwater housing connected rotatably to the gear housing, mountingmeans arranged between the gear housing and the underwater housing formounting the drive in a boat hull with the gear housing on the insideand the underwater housing on the outside of the hull and comprising anexhaust passage, which has an exhaust outlet opening into an exhaustinlet to an exhaust passage in the underwater housing, andpower-operated means which are connected to an electronic control unitand by means of which the underwater housing is rotatable relative tothe gear housing and the mounting means depending on control commandsfed into the control unit, wherein the exhaust outlet is surrounded by asurface layer which counteracts fouling by organisms present in thewater and the control unit is arranged so as, on a given controlcommand, via the power-operated means, to put the underwater housing ina predetermined position in which a surface of the underwater housing,which surface faces the exhaust outlet and surrounds the exhaust inlet,lies within the surface layer, wherein the control unit communicateswith an engine control unit for an internal combustion engine and isarranged so as, on a signal to the engine control unit to shut off theinternal combustion engine, to give a control command to thepower-operated means to put the underwater housing in the predeterminedposition.
 19. Outboard drive according to claim 18, wherein the controlunit is a control computer, in which the value of the steering angle ofthe underwater housing relative to the gear housing in the predeterminedposition is stored.
 20. Outboard drive for boats for driving at leastone propeller, comprising a gear housing, an underwater housingconnected rotatably to the gear housing, mounting means arranged betweenthe gear housing and the underwater housing for mounting the drive in aboat hull with the gear housing on the inside and the underwater housingon the outside of the hull and comprising an exhaust passage, which hasan exhaust outlet opening into an exhaust inlet to an exhaust passage inthe underwater housing, and power-operated means which are connected toan electronic control unit and by means of which the underwater housingis rotatable relative to the gear housing and the mounting meansdepending on control commands fed into the control unit, wherein theexhaust outlet is surrounded by a surface layer which counteractsfouling by organisms present in the water and the control unit isarranged so as, on a given control command, via the power-operatedmeans, to put the underwater housing in a predetermined position inwhich a surface of the underwater housing, which surface faces theexhaust outlet and surrounds the exhaust inlet, lies within the surfacelayer, wherein the underwater housing is rotatable between twopredetermined end positions and in that the surface layer covers thesurface region between these end positions, wherein the control unitcommunicates with an engine control unit for an internal combustionengine and is arranged so as, on a signal to the engine control unit toshut off the internal combustion engine, to give a control command tothe power-operated means to put the underwater housing in thepredetermined position.